Transforming growth factors (TGFs) produced by virally transformed and tumor cells are polypeptides that reversibly induce the transformed phenotype when added to normal cells. One class of TGFs, the i-TGFs, are active alone whereas a second class of TGFs, the d-TGFs, need the simultaneous presence of epidermal growth factor (EGF) to induce expression of the transformed phenotype. The action of TGFs is likely to be mediated by cell surface receptors. We provide preliminary evidence that i-TGFs interact simultaneously with the 170 kilodalton EGF receptor which possibly mediates cellular proliferation, and with a 60 kilodalton receptor which does not bind EGF and may mediate induction of the transformed phenotype. Here we propose a detailed study of putative targets of TGFs action mediated through both types of TGF receptors. The functional relationship between i-TGF and d-TGF purified from transformed cell lines will be tested based on their respective abilities to interact with the 60K receptor and other possible receptor types. The phosphorylation state of cellular phosphoproteins will be analyzed after cell exposure to i-TGF, d-TGF and EGF to identify putative intracellular targets of protein kinases modulated by TGFs. The phosphoamino acid contents of these phosphoproteins before and after exposure to TGFs will be documented. The possibility that specific cellular components are substrates of TGF action will be addressed using the appropriate monospecific antibodies. The possible effects of TGFs on their own receptor and on receptors for other growth factors, and vice versa, also will be addressed. From these protocols, we expect to gain information on the cellular components and steps directly involved in the phenotypes transformation induced by TGFs.